Economical miniaturized assembly and connection technology for LEDs and other optoelectronic modules

ABSTRACT

An economical miniaturized assembly and connection technology for LEDs and other optoelectronic modules is provided. A manufactured item in accordance with this technology includes a substrate with an optoelectronic component contacted in a planar manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. Section371 of International Application No. PCT/EP2004/052676, filed Oct. 27,2004, which published in German as WO 2005/050746 and which claimsbenefit of German Patent Application 103 53 679.5, filed Nov. 17, 2003.

BACKGROUND OF THE INVENTION

In the production of individual LEDs and lighting modules (compact lightsources) wire bonding and soldering, or mounting chips with conductiveglue, are predominantly used as technologies for electrical contactbetween a chip and a substrate. In this way, insertable components aswell as LED arrays for lighting modules are produced. The customaryassembly process is as follows:

-   -   die bonding: placing of the chip(s) in a filled conductive glue        (gluing) and hardening of the glue or    -   mounting of the chip with the aid of a solder under temperature        and possibly pressure (soldering/alloying),    -   wire bond: electrical connection of the chip by wire contact,    -   encapsulation of the chip with transparent material (epoxy,        silicone, acrylate, polyurethane, and other polymers) by casting        or injection technology,    -   producing individual parts by sawing, water-jet cutting, or        laser separation.

SUMMARY OF THE INVENTION

In the development of miniaturization, smaller and smaller componentheights are being demanded on the market. Along with this, themanufactured items must be economical and offer sufficient reliability.In the case of chip arrays even very high reliability is required.Moreover, the connection technology should offer great flexibility inorder to be able to react quickly, flexibly, and economically to designchanges.

Proceeding from this, the objective of the invention is to specifymodules with a substrate and optoelectronic components, as well asprocesses for their production, which satisfy these requirements.

This objective is realized by the inventions specified in theindependent claims. Advantageous developments follow from thesubordinate claims.

Accordingly, a substrate has an optoelectronic component which iscontacted thereto in a planar manner. The contacting is therefore nolonger accomplished by thick wires, in given cases running at a distancefrom the substrate and component, but rather by a planar, flat, evenconducting structure approximately in the form of a copper layer.

By virtue of contacting in a planar manner, an especially small heightof the module consisting of the substrate and optoelectronic componentcan be achieved.

The optoelectronic component can, for example, be contacted by otheroptoelectronic components on the substrate. In particular, it iscontacted in a planar manner by conducting elements, e.g. printedconductors, of the substrate.

In order to run the planar contact at as small a distance from thesubstrate and/or optoelectronic component as possible, the substrateand/or the optoelectronic component are provided, at least partially,with an insulating layer on which the planar conducting structure isdisposed for planar contacting of the optoelectronic component.

The insulating layer can be formed by a foil, enamel, and/or a polymerlayer. The layer can be laminated, vapor deposited, printed, and/orsprayed. Structuring of the insulating layer can be done, for example,by means of laser structuring, (plasma) etching structuring, inkjetstructuring, and/or photostructuring. As a polymer, parylene inparticular can be used.

In the optoelectronic component an interaction of light with theenvironment should be possible. This can be realized particularlyadvantageously in two ways.

In one, the insulating layer as a whole, or in particular an area of thelight entry and/or exit opening of the optoelectronic component, can be(highly) transparent.

In the other, a window can be opened in the insulating layer in the areaof the light entry and/or exit opening of the optoelectronic component.The window can, e.g. if the insulating layer is formed by a foil,already be present in the layer before its application. Alternativelyhowever, it can also be opened after the application of the layer bycorresponding structuring of the layer by means of the aforementionedprocedures.

Such a window is preferably provided in the insulating layer also in thearea of one or more electrical contact points of the optoelectroniccomponent. The planar conducting structure can be led through the windowto the contact point of the optoelectronic component.

If this is planned, the insulating layer and/or the planar conductingstructure can also cover, at least partially, a light entry and/or exitopening of the optoelectronic component.

For this, the planar conducting structure is embodied to be reflectingso that, for example, light is reflected back into the optoelectroniccomponent and can leave at another light exit opening. Thus, the planarcontact can cause light guidance in addition.

The optoelectronic component is, for example, an LED, in particular anOLED, and/or a photovoltaic component. As substrate a printed circuitboard, a ceramic element, a Flex, in particular laminated on both sideswith cooper, a punched or etched lead frame, or a layer structure can beused, as, for example, in the production of chip cards or flexiblecircuits.

Preferably, the height of the manufactured item with a substrate and anoptoelectronic component is less than 0.4 mm.

In a process for producing a manufactured item comprising a substratewith an optoelectronic component the optoelectronic component iscontacted in a planar manner. Advantageous developments of the processfollow analogously to the advantageous developments of the manufactureditem and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of the invention can be inferred fromthe description of embodiment examples with the aid of the drawings.Therein

FIG. 1 shows a section through a manufactured item comprising asubstrate with an optoelectronic component contacted in a planar manner,

FIG. 2 shows a section through an alternative manufactured itemcomprising a substrate with an optoelectronic component contacted in aplanar manner,

FIG. 3 shows a comparison between an optoelectronic component contactedin a planar manner and in a traditional manner in plan view, and

FIG. 4 shows a comparison between the optoelectronic component contactedin a planar manner and in a traditional manner in relation to the lossof light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, several characteristics of assembly and connection technologywill be presented.

One or more optoelectronic components, e.g. in the form of chips, arefixed on a substrate by gluing or soldering. The electrical connectionof contact points in the form of contact pads on the upper side of theoptoelectronic components is then achieved through a planar contactingprocess. This can be based, for example, on the lamination of anelectrically insulating foil and contacting by planar conductingstructures in the form of metal structures on this foil. Instead ofbeing in the form of an insulated foil, an insulated layer can also beproduced by other processes, such as enameling, vapor deposition, orprinting.

For the insulating layer in the form of insulating foil:

-   -   Application, for example, through isostatic lamination in an        autoclave, through the use of a hot roll laminator, or in a        vacuum hot press.    -   The foil can be transparent in the wave length range of the        light emitted from or absorbed by the optoelectronic component.        Then, no partial removal of the foil is necessary. The foil can        then also take over the protective function of the clear mold        compound.    -   If the foil is not sufficiently transparent, it can be        structured so that the light exit on the chip flanks and/or on        the upper side of the chip is maximized according to LED type.        This can be done, for example, flexibly and independent of the        topography by means of laser ablation.    -   By suitable laminating processes the insulating foil can be made        to reproduce the chip surface. With this, it can be achieved        that there is fill insulating function to increase reliability        even at the edges and in the corner areas.

For contacting by planar conducting structures in the form of metalstructures there are various possibilities:

-   -   Electrical connection by a suitable metallization process, e.g.        application of a thin starting layer by means of sputtering or        vapor deposition, followed by selective reinforcement with        currentless or galvanic deposition, e.g. by copper.    -   The insulating foil is coated in an electrically conductive        manner, e.g. by lamination of a metal foil. This metal foil is        then structured before or after the lamination process. The        connection between chip and metal structure can be done with        raised, in particular rough, bumps on the chip pads by        mechanical pressing or also by partial galvanic or currentless        deposition. In this case, finishing of the aluminum chip pad on        the wafer plane is advantageous.    -   The connection can also be made by the use of preformed pressing        tools in commercially available presses.    -   The conductive metal structures can be applied by a printing        process.

FIG. 1 shows a manufactured item 1 comprising a substrate 2 in the formof an etched copper lead frame. Therein the copper of the lead frame isencircled with a nickel-gold plating in order to improve its solderingproperties. On the substrate 2 an optoelectronic component 3 is disposedin the form of a chip and electrically and mechanically connected to thesubstrate 2 by the conductive glue or solder 4.

An insulating layer 5 in the form of a foil is led over the substrate 2and the optoelectronic component 3. The insulating layer 5 is opened bya window in the area of the light exit opening of the optoelectroniccomponent 3. To contact the optoelectronic component 3, a planarconducting structure 6 in the form of a metallization is led over theinsulating layer 5 to contact points of the optoelectronic component 3and to a printed conductor 7 of the substrate 2.

The substrate 2 with the optoelectronic component 3, the insulatinglayer 5, and the planar conducting structure 6 are molded into aprotective mass 8 in the form of a clear mold compound. The manufactureditem 1 is approximately 150 μm high.

The manufactured item 1 represented in FIG. 2 corresponds to that inFIG. 1 except that the insulating layer 5 is embodied so as to betransparent and thus runs through in the area of the light exit openingof the optoelectronic component 3. Therefore, no window is open therebut rather only at the contact points of the optoelectronic component 3where it is electrically connected to the planar conducting structure 6.The transparent insulating layer 5 can, in particular in the area of thelight exit opening of the optoelectronic component 3, contain pigmentsin order to color the exiting light.

FIG. 3 shows, at the left of he figure, an optoelectronic component 3contacted in a planar manner with a large central light exit and an edgecontact which completely encircles this light exit and comprises aplanar conducting structure 6 and an insulating layer concealedthereunder. Alternatively, the edge contact can, depending on the layoutof the contact points of the optoelectronic component 3 and intendedlight guidance, also not be completely encircling but rather only run atone or more individual points to a side of the optoelectronic component3, specifically the face side opposite the substrate 2.

FIG. 3 shows, at the right of the figure, an optoelectronic component 3which is contacted according to the state of the art by 120-μm wirebonding with a wire 9. As can be seen, a large part of the light exitopening of the optoelectronic component 3 is covered.

The advantages of the planar contact in light guidance becomeparticularly clear in FIG. 4. There one once again sees at the left andon the substrate 2 the optoelectronic component 3 contacted in a planarmanner by the insulating layer 5 and the planar conducting structure 6.All the light exit openings of the optoelectronic component 3 where alight exit is not desired are covered by the insulating foil 5 and theplanar conducting structure 6. If they are embodied so as to bereflecting, then the light is even reflected back into theoptoelectronic component 3 until it exits at the light exit openingprovided.

In contradistinction to this, in the case of contacting according to thestate of the art and represented at the right in FIG. 4 a large part ofthe desired light exit area is covered by the connected wire 9. Ratherthan there, the light exits in an undesired manner parallel to thesubstrate 2 from the sides of the optoelectronic component 3.

In the case of the optoelectronic component 3 contacted in a planarmanner on the contrary, the light exits as desired at a face of theoptoelectronic component 3, specifically the front face opposite thesubstrate 2, and along with this approximately perpendicular to thesubstrate 2.

The described assembly and connection technology comprises the followingsteps:

-   -   Small-surface contacting and a variable layout make possible the        largest possible light yields.    -   Homogenous current distribution by selected contact conductor        dimensions with a high light yield as a consequence.    -   Ultra-thin, miniaturized structure.    -   Planar contacting makes possible thin mold mass covering.    -   Planar contacting makes possible an effective dissipation of        heat by a cooling element mounted in a flat manner.    -   Economical assembly and connection technology by highly parallel        processing (processing in use). Manufacture in the reel-to-reel        process is also possible.    -   No shadowing by central wire bond pads in the center of the        chip.    -   High reliability by adapted material properties, e.g. CTE        (coefficient of thermal expansion), Tg (glass transition        temperature), and so on.    -   With suitable choice of the optical properties of the insulating        foil it can assume the protective function of the clear mold        compound so that the clear mold compound is no longer necessary.    -   The luminescent materials for the blue-to-white light conversion        can be introduced as pigments into the foil. In this way good        control of the color coordination is possible by a precisely        specified foil thickness and pigment concentration in the foil.

1. An article of manufacture comprising: a substrate having a substratecontact; an optoelectronic component having a central light exit and/orentry and an edge contact disposed at lease partially around a peripheryof the light exit; an insulating layer partially arranged on thesubstrate and the optoelectronic component; and a conducting structurearranged on the insulating layer so as to contact the edge contact andthe substrate contact, wherein a window is opened in the insulatinglayer in the area of the central light exit and/or entry of theoptoelectronic component.
 2. The article of manufacture according toclaim 1, wherein the substrate contact is a printed conductor.
 3. Thearticle of manufacture according to claim 1, wherein the insulatinglayer comprises one or more of a foil, enamel, and a polymer layer. 4.The article of manufacture according to claim 1, wherein in theinsulating layer in the area of a contact point for the optoelectroniccomponent a window is opened through which the planar conductingstructure is led to the contact point of the optoelectronic component.5. The article of manufacture according to claim 1, wherein theinsulating layer contains pigments to color the light emitted from orabsorbed by the optoelectronic component.
 6. The article of manufactureaccording to claim 1, wherein the planar contact at least partiallycovers a light exit and/or entry opening of the optoelectroniccomponent.
 7. The article of manufacture according to claim 1, whereinthe optoelectronic component comprises one or more of an LED, an OLED,and a photovoltaic component.
 8. The article of manufacture according toclaim 1, wherein the substrate is one of: a printed circuit board, aFlex, and a lead frame.
 9. The article of manufacture according to claim1, wherein the height of the article of manufacture is less than 0.4 mm.10. A method of making an article of manufacture according to claim 1,the article of manufacture comprising a substrate and an optoelectroniccomponent, the method comprising contacting the optoelectronic componentin a planar manner.
 11. The article of manufacture according to claim 1,wherein the conducting structure at least partially covers the lightexit and/or entry of the optoelectronic component, the conductingstructure being reflective so as to guide light.
 12. The article ofmanufacture according to claim 1, wherein the insulating layer comprisesparylene.
 13. The article of manufacture according to claim 1, whereinthe conducting structure comprises a metal foil being arranged by alamination process.
 14. An article of manufacture comprising: asubstrate having a substrate contact; an optoelectronic component, saidoptoelectronic component having a central light exit and/or entry and anedge contact disposed at least partially around a periphery of the lightexit; and a conducting structure, arranged on the optoelectroniccomponent and the substrate so as to contact the edge contact and thesubstrate contact, wherein the conducting structure at least partiallycovers the light exit and/or entry of the optoelectronic component, theconducting structure being reflective so as to guide light.
 15. Thearticle of manufacture according to claim 14, further comprising anelectrically insulating layer contacting the optoelectronic component,on which the planar conducting structure is disposed.
 16. The article ofmanufacture according to claim 15, wherein the electrically insulatinglayer has a window formed in an area of the light exit and/or entry. 17.The article of manufacture according to claim 15, wherein theelectrically insulating layer has transparent portion formed in an areaof the light exit and/or entry.
 18. The article of manufacture accordingto claim 15, wherein the insulating layer contains pigments for coloringthe light emitted or absorbed by the optoelectronic component.
 19. Thearticle of manufacture according to claim 14, wherein the conductingstructure is a metallic layer.